Vaso-occlusive devices or implants are used for a wide variety of reasons, including treatment of intra-vascular aneurysms. Commonly used vaso-occlusive devices include soft, helically wound coils formed by winding a platinum (or platinum alloy) wire strand about a “primary” mandrel. The coil is then wrapped around a larger, “secondary” mandrel, and heat treated to impart a secondary shape. For example, U.S. Pat. No. 4,994,069, issued to Ritchart et al., which is fully incorporated herein by reference as though set forth in full, describes a vaso-occlusive device that assumes a linear, helical primary shape when stretched for placement through the lumen of a delivery catheter, and a folded, convoluted secondary shape when released from the delivery catheter and deposited in the vasculature.
In order to deliver the vaso-occlusive devices to a desired site in the vasculature, e.g., within an aneurysmal sac, it is well-known to first position a small profile, delivery catheter or “micro-catheter” at the site using a steerable guidewire. Typically, the distal end of the micro-catheter is provided, either by the attending physician or by the manufacturer, with a selected pre-shaped bend, e.g., 45°, 26°, “J”, “S”, or other bending shape, depending on the particular anatomy of the patient, so that it will stay in a desired position for releasing one or more vaso-occlusive device(s) into the aneurysm once the guidewire is withdrawn. A delivery or “pusher” assembly is then passed through the micro-catheter, until a vaso-occlusive device secured to a distal end of the pusher assembly is extended out of the distal end opening of the micro-catheter and into the aneurysm. The proximal end of the vaso-occlusive device is typically secured to the distal end of the pusher assembly with an adhesive at what is known as a “major junction” of the vaso-occlusive device delivery assembly.
Another vaso-occlusive device delivery assembly major junction design is disclosed in U.S. Pat. No. 8,202,292, issued to Kellett, which is fully incorporated herein by reference as though set forth in full. The major junction includes a flat adapter connecting a delivery wire to a vaso-occlusive coil. The delivery wire has a hook or “J” shape distal end configured to be received in an aperture in the proximal end of the adapter to attach the delivery wire to adapter. The vaso-occlusive coil has windings that define openings configured to receive fingers in the distal end of the adapter to attach the vaso-occlusive coil to the adapter. Consequently, the adapter facilitates attachment of the delivery wire to the vaso-occlusive coil.
Once in the aneurysm, segments of some vaso-occlusive devices break off to allow more efficient and complete packing. The vaso-occlusive device is then released or “detached” from the end of the pusher assembly, typically by detaching a distal end of the pusher assembly. Then the pusher assembly is withdrawn back through the catheter. Depending on the particular needs of the patient, one or more additional occlusive devices may be pushed through the catheter and released at the same site.
One well-known way to release a vaso-occlusive device from the end of the pusher assembly is through the use of an electrolytically severable junction, which is a small exposed section or detachment zone located along a distal end portion of the pusher assembly. The detachment zone is typically made of stainless steel and is located just proximal of the vaso-occlusive device. An electrolytically severable junction is susceptible to electrolysis and disintegrates when the pusher assembly is electrically charged in the presence of an ionic solution, such as blood or other bodily fluids. Thus, once the detachment zone exits out of the catheter distal end and is exposed in the vessel blood pool of the patient, a current applied through an electrical contact to the conductive pusher completes an electrolytic detachment circuit with a return electrode, and the detachment zone disintegrates due to electrolysis. Other detachment mechanisms for releasing a vaso-occlusive device from a pusher assembly include mechanical, thermal, and hydraulic mechanisms.
While major junctions secured with an adhesive and those including a flat adapter have performed well, connections between the delivery wire, the vaso-occlusive coil, and the adapter can be improved. Accordingly, there remains a need for other systems and methods for securing a vaso-occlusive device to a pusher assembly at a major junction.